Those skeletons and mosters were trying to protect Carrot Top and Derpy from the Ghost mare, the true villain. Now, Carrot Top, under the Ghost mare's spell (touching her trail)is getting her sould drained. The skeletons are protecting Derpy from suffer the same fate blocking the ice.
Derpy watched her friend get lifted into the air, terrified sadness and panic washed over her as she saw the lifeblood get sucked out by what was their "savior". She knew there was nothing she could do without some kind of counter magic, which she did not possess. She knew she would be next if she didn't run or fly as fast as she could out.
The evil ghost mare began to shoot beams of ice her way. Derpy, quickly sidestepping, missed the frigid ray by a feather, and her side began to burn from the cold. She began to run.
The ground underneith her began to move and objects began to emerge from the ground; the skeletal remains of ponies past. Derpy let out a cry of fear, for she feared these animated corpses were after. She closed her eyes, prepared for pain.
When pain did not come, she dared a peak. There were three skeletons in front of her. Surely more came out, right? She glanced behind her; a throng of skeletons was there, and their stance seemed to show that they were challenging the evil in front of them. The being that once was a mare seemed enraged, shooting ice beams at them. Several skeletons were encased in hard ice.
One ice beam was headed straight for Derpy. Derpy let out a bray of fear, fearing she would be encased in hard ice. One skeleton jumped right in the beam's way, and received the full brunt of the attack, becoming an ice statue. Were these living dead trying to protect her?!
She felt her mane and wings tug. She turned her focus in front of her; two of the three skeletons in front of her were tugging on her with their teeth, the third hopping impatiently. There was an air of urgency about them, as if they were conveying a deep concern for her safety. They seemed to want her to run. A quick glance behind: another skeleton jumped in front of an ice beam headed her way, and so she ran.
She followed the three urgent skeletons, with the hoard following close behind, blocking every beam aimed for the Pegasus. They ran through a maze, twisting and turning, almost losing her way, but other skeletons pulled her back.
In the more dark parts of the maze, there was a slight glow about them, in the form of...fully fleshed ponies? Through every twist and turn they took, she saw them clearer and clearer. They appeared to be the trapped souls, unable to leave this place, or their bodies, and would not let others resign to the same fate. They all wore the same expression: concern and fear.
The hoard behind was almost gone, danger clearly coming closer. The skeleton in front, the one that was hopping, stopped and pointed a hoof towards a gleam of light.
(There!) it somehow said (There is you chance to get out!)
(Fly as fast as you can!) another said (we'll keep her busy long enough!)
Derpy didn't question. Completely exhausted, and adrenalin fueled, bolted off the ground and towards the light. She heard the ghost mare cry out, bones rattling, and a struggling battle, but she didn't look back. Tears streaming down her face, she made a straight beeline for the light.
She still had a ways to go when she heard a mighty roar and bones snapping and landing hard; the ghost mare had broken free. Derpy flapped harder, if her heart was pounding any harder, it'll jump out of her chest and run away.
The tips of her back hooves started to feel cold and begin to hurt, that evil was gaining. It would be close...
The cold began to take her over when POW!! She whizzed past a thin layer of dried grass and into the open sunset. She heard a shriek, then silence. She kept flapping hard until she reached the clouds, but when relief and sadness and exhaustion hit her, it hit her hard. She could no longer keep herself in the air, and she plummeted. Past the rainbow, past the clouds to the ground where a lake rested. Tears blurring her vision, the sensation of falling numb to her, she choked out three words: